1. Field of the Invention
The present invention relates to a thin film magnetic head used for a magnetic disk device or the like.
2. Description of the Prior Art
A construction of a thin film magnetic head of this kind in the prior art will be described with reference to FIGS. 6 and 7.
In these figures, reference numeral 1 designates a substrate formed of non-magnetic material (such as glass, ceramics, etc.); 2 and 3 upper and lower magnetic layers formed of magnetic material (such as Permalloy, Sendust, amorphous alloy, etc.); 4 a magnetic insulating layer formed of non-magnetic material (such as SiO.sub.2, Al.sub.2 O.sub.3 or resin); 5 a protective layer formed of non-magnetic material (such as SiO.sub.2, Al.sub.2 O.sub.3 or resin); and 6 a conductive coil formed of a conductive material (such as gold, silver, copper, aluminum, etc.). The thin film magnetic head is formed by a method which comprises forming the lower magnetic layer 3 on the substrate 1 using a method such as sputtering, forming the magnetic insulating layer 4 on the lower magnetic layer 3 using sputtering or the like and forming the conductive coil 6 within the magnetic insulating layer 4, and further successively forming the upper magnetic layer 2 and the protective layer 5 using sputtering or the like to thereby form a gap G on a gap surface 7.
In the operation of the thin film magnetic head constructed as described above, in the case where a signal is recorded in a magnetic recording medium (not shown), a signal current is applied to the conductive coil 6 to thereby magnetize the upper and lower magnetic layers 2 and 3, and the magnetic flux is outside the thin film magnetic head in the gap on the gap surface 7 of the thin film magnetic head to record a signal in a magnetic recording medium (not shown) adjacent to the gap surface 7 as a change of a magnetic pole. Conversely, in the case where a signal recorded in the magnetic recording medium is reproduced, a signal recorded as a change of the magnetic pole on the magnetic recording medium is detected at the gap G whereby the magnetic field in the upper and lower magnetic layers 2 and 3 is changed. A current is produced in the conductive coil 6 sandwiched between the upper and lower magnetic layers 2 and 3 due to the electromagnetic induction caused by the change of the magnetic field, and the current is sent to outside the thin film magnetic head as a signal.
In the above-described thin film magnetic head, recording and reproduction of a signal to the magnetic recording medium are carried out by one and the same gap G. However, the spacing (gap width) of the gap G suitable for recording operation and the gap width suitable for reproduction are in the relationship contrary to each other. That is, the narrower the gap width at the time of reproduction with respect to the recording wavelength of the signal on the magnetic recording medium, the smaller the frequency loss at the time of reproduction, and the reproduction efficiency is improved. Conversely, at the time of recording, the narrower the gap width with respect to the recording wavelength, the larger the gap loss at the time of recording, and the recording efficiency lowers. Therefore, in the actual thin film magnetic head, the gap width so as to minimize the lowering of the reproduction efficiency and the recording efficiency has to be set and the operation efficiency of the thin film magnetic head is to be lowered, posing a great obstruction in providing a high resolving power.
The present invention has been achieved in view of the aforementioned point. It is an object of the present invention to provide a thin film magnetic head in which two kinds of gaps are formed whereby the operating efficiency, particularly the operating efficiency during reproduction, is improved and high resolving power is provided.